1. Field of the Invention
The present invention relates to the field of Radio Frequency Identification (RFID), and more particularly, to an RFID tag device which communicates with an RFID reader.
The present invention is derived from the research performed as a part of the information technology (IT) new growth power core technology development business, which was hosted by the Ministry of Information and Communications Republic of Korea (MIC) and the Institute for Information Technology Advancement (IITA) [Task management No.: 2005-S-106-02, entitled “Development of Sensor Tag and Sensor Node Technologies for RFID/USN”].
2. Description of the Related Art
A Radio Frequency Identification (RFID) is a process or chip which puts information about processes of producing, distributing, storing, and selling products into a tag attached to the products, has its own antenna, makes a RFID reader read the information, and connects with an artificial satellite or uses mobile communication in order to access an information system.
Meanwhile, a RFID system includes a tag and a reader, wherein the tag stores information and exchanges data according to a protocol and the reader communicates with the tag.
The RFID tag can be classified into an active type and a passive type, wherein the active type needs a power source and uses a direct power supply, and the passive type is operated by an electromagnetic field of the reader without power being supplied directly from inside or outside of the RFID tag. By using the active type, required power for the reader is reduced and an identification distance may be far from the reader. However, since a power supply device is needed, the operation time is limited and the cost of the active type is more expensive than the passive type. On the other hand, the passive type is lighter than the active type, the cost of the passive type is less than the active type, and the passive type can be used semi-permanently. However, when the passive type is used, an identification distance is short and more power is consumed by the reader, compared to when the active type is used.
In addition, a battery powered passive tag, which combines the active type and the passive type, has been suggested.
According to the conventional battery powered passive tag, a non-volatile memory is generally used as a storing means for stability of data. However, the amount of power consumption is large and thus, the life of the tag is reduced. In particular, such a problem arises more seriously in a sensor tag which is generally used in a ubiquitous sensor network (USN). That is, the sensor tag periodically stores various environmental factors measured by the sensor, for example, temperature and humidity, in the non-volatile memory. The power source used for such a process is supplied from the internal battery, instead of the RF power transmitted from the reader, and so, when the battery is used up, data can no longer be stored.